High pressure pump for all liquids

ABSTRACT

A device enables the pumping of any kind of liquid while giving the liquid very high delivery pressure. The units that cause pumped liquid suction and then its delivery are driven exclusively by hydraulic means excluding mechanical means. So that there is no material contact between the driving units and the pumped product and that the product cannot damage the mechanical driving units, the chamber receiving the hydraulic fluid is, at the end of each compression cycle, placed again in direct communication with the hydraulic fluid reservoir.

BACKGROUND

This invention relates to a pump intended for high pressure pumping anddelivery of almost any liquid such as water, petrol, gas oil, oils,corrosive chemical liquids and sludge, but more particularly for thehigh pressure supply of fuel injectors for internal combustion engines.

Low pressure pumps are known for liquids of this type, and are generallycentrifugal pumps, gear pumps, sometimes piston pumps or other types ofpumps. With these known pumps, a high delivery pressure (in excess of 50bars) either cannot be obtained or only with great difficulty and atgreat expense due to the fact that, once one starts using highpressures, the moving parts begin to seize and substantial leakingoccurs due to the often very low viscosity of the liquids pumped.

To avoid such seizure or leakage, diaphragm pumps have been known to beused, in which case it becomes impossible to achieve high deliverypressure. In fact, the diaphragm is driven by a mechanical means (cam,lever or the like) on one side, and is subjected on the other side tothe delivery pressure: it ensures that, once the pressure becomes high,the diaphragm deteriorates at the points where mechanical stress isapplied.

Also known, to pump special liquids such as corrosive liquids, is theassociation of two pumps: a first pump which is a hydraulic pump thatdelivers and draws back a hydraulic liquid which, by way ofreciprocating motion, drives the mobile elements of a second pump whichdraws in and pressurizes the liquid to be pumped. These mobile elementswhich ensure physical separation of the hydraulic liquid and the liquidto be pumped, though driven in reciprocating motion by the hydraulicliquid, are either deformable diaphragms or free-floating pistons.

The free-floating pistons are defective from the point of view oftightness, and this defect cannot be overcome when absolute tightness isrequired. If a seal is fitted between the free-floating piston and thecylinder in which it moves, perfect tightness cannot be obtained. If theseal is eliminated, either there will be a very thin film of oil betweenthe friction surfaces and therefore micro-leakage, or the rubbingsurfaces will heat up if there is no film of oil. In the particular caseof high pressure fuel injection, no leakage, no matter how small, can betolerated and, of course, heating is liable to cause an explosion.

The known free-floating piston-type devices, such as e.g., U.S. Pat. No.4,443,160, must therefore be ruled out.

The invention thus relates to a pumping device in which the mobileelements—to which a reciprocating pumping motion is imparted by thehydraulic pump and which ensure a perfectly tight separation between thehydraulic “driving” liquid and the liquid to be pumped—are deformablediaphragms.

Generally, this type of deformable diaphragm pump has at least one ofthe following drawbacks and sometimes several simultaneously:

a—if the separating and pumping diaphragm is mechanically linked to thepiston of the hydraulic pump, there is not equal pressure on both sidesof the flexible diaphragm as a result of which the latter will not lastover time, it will deteriorate;

b—if the diaphragm is completely free, i.e., unattached to any drivemechanism and driven solely by the hydraulic liquid delivered by thepump, there will be equality of pressure on the two sides of thediaphragm. However, due to inevitable leaks, even very minute ones, thevolume of hydraulic liquid delivered increases with each cycle andultimately exceeds the volume the diaphragm can deliver; this causes ahydraulic blocking which creates so much excess pressure that one orother of the pumps breaks. In the particular case of high pressure fuelinjection, if the element that breaks is the element delivering thefuel, fire will inevitably break out,

c—in both eases, i.e., whether the diaphragm is attached to the pistonor unattached, if the volume of hydraulic liquid continually being drawnin and delivered is constantly the same, the diaphragm will heat up as aresult of the indefinitely repeated compression cycles, until it reachesa temperature such that the diaphragm(s) break.

U.S. Pat. No. 4,392,787 granted to Notta discloses a unit including ahydraulic slanted plant pump, each piston of the pump being associatedat its end with a flexible diaphragm which is connected to a rod thatslides inside the piston. This device has the drawbacks described abovein “a” and “c”. The volume of liquid continually pressurized is alwaysthe same and will therefore heat up. Moreover, the inevitable littleleaks are offset by the intake of additional oil via a non-return valve,but should a substantial leak accidentally occur, the piston will comeinto mechanical contact with the diaphragm thus destroying the latter.

U.S. Pat. No. 2,960,936 granted to Dean describes a pump in which acompletely unattached diaphragm is cyclically pressed and released by ahydraulic volume displaced by a cam-driven piston. This device hasdrawbacks “b” and “c”. If, for any reason, the supply were to be stoppedor slowed down, the diaphragm would not completely redeploy itself and acorresponding quantity of hydraulic liquid would be introduced at eachcycle until the occurrence of breakage (drawback “b”). Furthermore, asthe volume of hydraulic liquid compressed is always the same, heatingwill inevitably take place (drawback “c”).

German Patent No. 2,447,741 granted to Wanner discloses a diaphragm pumpmechanically linked to a piston which slides inside a hydraulic pumppiston. The drawbacks are the same as for above-mentioned U.S. Pat. No.4,392,787.

SUMMARY OF THE INVENTION

To remedy these drawbacks, the invention provides a device in which eachdiaphragm is unattached and in which, at the end of each piston cycle,the “dead” chamber situated downstream of the top dead center of thispiston (position of maximum compression), in which the liquid is incontact with the diaphragm, is made to communicate with the reserve ofhydraulic liquid; as a result, the liquid situated in the chamber isforced back towards this reserve firstly by the expansion of the liquidand then by the forcing effect of the diaphragm which is held incountercheck by a spring.

We thus obtain, on the one hand, a continuously repeated heat exchangebetween the compressed liquid and the liquid that is not compressed,and, on the other hand, a return of the diaphragm to its initialposition at each cycle or, in other words, a suppression of any increasein volume of the hydraulic liquid acting on the diaphragm, increase thatis inevitably caused on an on-point basis by leaks; this is because itis not possible to manufacture a high pressure hydraulic pump withpistons, which does not heat up and which has a satisfactory, leak-freeoutput.

According to a first object, the invention relates to a pump enablingany type of liquid to be pumped while imparting a very high deliverypressure thereto, of the type comprised by the association of two pumps:on the one hand, a hydraulic pump, and, on the other hand, a second pumpin which the mobile means performing the suction and delivery of theliquid to be pumped, are flexible diaphragms to which reciprocatingmotion is imparted, first in one direction and then in the other, by thedisplacement of the hydraulic liquid pumped then drawn back by the firstpump. The pistons of the first pump are tubular and passed through bythe hydraulic liquid which, during the suction phase, passes through acrescent or groove hollowed out in the surface of the slanted plate orcam. The deformable diaphragms each are held in countercheck by a springin such a way that, at the end of the compression stroke of each piston,communication is established between the chamber in which the hydraulicliquid finds itself forced against the diaphragm, and the suctionchamber, this liquid being, on the one hand, sucked up by the motion ofthe piston and forced back by the diaphragm under the effect of itsspring action, thus ensuring, on the one hand, an exchange between thehydraulic liquid heated by compression and the unheated liquid, and, onthe other hand, the return of the diaphragm to its initial position.

The pump embodying the invention can also include one or other of thefollowing arrangements:

a—the second pump comprises as many volumes or bores as the first pumphas bores, each bore of the second pump communicating directly with thecorresponding bore of the first pump so that each piston of the firstpump cyclically delivers and draws the hydraulic liquid into thecorresponding bore of the second pump;

b—each bore of the second pump is divided into two parts by a deformablediaphragm held in countercheck by a spring, the part communicating withthe corresponding bore of the first pump receiving the hydraulic liquiddelivered and drawn back by the first pump, and the other part, which isfitted with suction and delivery valves, performing suction and deliveryof the product to be pumped;

c—the chamber in which the piston heads move back and forth is connectedto a reservoir of hydraulic liquid;

d—the reservoir of hydraulic liquid is on the exterior of the first pumpand communicates with the latter by means of a pipe leading into thechamber;

e—the pump embodying the invention is destined for the high pressuresupply of fuel injectors for internal combustion engines, and thehydraulic liquid of the first pump (I) can be the oil of the engine.

According to a second object, the invention relates to a means enablingvariation of the cubic capacity of the first pump and therefore of theflow rate of fuel towards the injection devices.

This means is either the arrangement of a slated plate of variableinclination or the arrangement of a means, in the pistons of thehydraulic pump, having as function to short-circuit all or part of thevolume of hydraulic liquid introduced into the bore during the suctionphase.

According to the invention, each tubular piston of the hydraulic pump isfitted with holes that can be totally or partly obstructed by a mobileliner, all the mobile lines being moved together by a control unitdriven by the operating conditions of the engine.

This device can furthermore comprise one or other of the followingarrangements:

a—the pistons slide in two support members drilled with orifices, thetwo support members being separated from one another by an annularspace, constituting a chamber, in which the liners moved between twoextreme positions: in one of these positions, as the orifices are notobstructed by the liner, all the liquid delivered by each piston flowsback into the annular chamber via the orifices of the piston as the pump(I) rate is zero; in the other of these positions, as all the orificesare covered by the liners, each piston forces back all the hydraulicliquid drawn in, the flow rate of the pump then being at maximum.

b—the liners can be in all intermediate positions included between thetwo extreme positions, as a result of which the flow rate of the pump(I) can be set at all values included between zero and the maximum rate.

c—the liners are coupled to a common control unit which is driven by anycontrol device appropriate for the regulation of the high pressure flowof fuel as a function of the engine supply requirements without anyreflux of high pressure fuel to the reservoir.

d—a damping device can be located downstream of the outlet of the secondpump (II) and upstream of the injectors to cancel the pulsation effectbrought about by the first pump (I).

e—the damping device can be a capacity of sizable volume in relation tothe fuel rate, maintained at the injection pressure by any appropriatemeans and can behave substantially in the manner of a hydromechanicalaccumulator.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will be apparent fromembodiments of the invention described, by way of non-limiting examples,in reference to the corresponding accompanying drawings in which:

FIG. 1 is a longitudinal cross-section of a first embodiment of theinvention;

FIG. 2 is a transversal cross-section according to A—A in FIG. 1;

FIG. 3 is a longitudinal cross-section of the variable-rate double pump,the parts being in the position corresponding to the maximum flow rate;

FIG. 4 is a view of the double pump in FIG. 3, the parts being in theposition corresponding to the zero flow rate;

FIG. 5 is a view along A—A of the face of the slanted plate in FIGS. 3and 4;

FIG. 6 is a longitudinal cross-section of the pump in FIG. 1 in whichthe individual diaphragms have been replaced by a single diaphragm;

FIG. 7 is a cross-sectional view along A—A of FIG. 6;

FIG. 8 is a cross-sectional view along B—B of FIG. 6;

FIG. 9 is a longitudinal cross-section of another embodiment of the pumpin which the suction valves have been eliminated;

FIG. 9a is a detailed view of part of FIG. 9, on a larger scale;

FIG. 10 is a longitudinal cross-section of the pump in FIG. 6 fittedwith the diaphragm suction system of FIG. 9;

FIG. 11 is a view of another embodiment in which the hydraulic pump is aradial pump.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In reference to FIGS. 1 and 2, the device embodying the invention can beseen to comprise a first pump, designated by the general reference “I”,and a second pump designated by the general reference “II”.

The first pump I is a pump with axial pistons driven in reciprocatingto-and-fro motion by a slanted plate 1.

The slanted plate 1 is integral with a primary shaft 2 (driven by anymeans not represented) borne by bearings 3. A plurality of tubularpistons bear against the slated face of the plate 1, each by means of asliding contact piece 5 drilled through at its center by a bore 6. Eachpiston 4 is held against its contact piece by a spring 7. A crescent 8is engraved on the front side 1. When the shaft 2 is driven in rotation,the slated plate 1, the contact pieces 5 and the spherical heads 4 a ofthe pistons 4 move back and forth in the chamber 9. The chamber 9 opensout, via a plurality of bores 22 passing through the case 21 of the pumpI, into a reservoir 11. This reservoir 11 is constituted by acylindrical envelope 23 surrounding the case 21.

When the primary shaft 2 rotates, the face of the slanted plate 1oscillates in the chamber 9 in such a way that the pistons 4 are drivenin reciprocating to-and-fro motion: in the direction corresponding tosuction, the pistons 4 are driven by their spring 7, and in the otherdirection, corresponding to pressurized delivery, they are thrust backagainst the spring 7 by the slanted plate 1. During the suction phase,the hydraulic liquid in the chamber 9 passes into the pistons 4 via thecrescent 8 and the bore 6 in each contacting piece 5.

This type of pump is known and described in numerous prior patentsgranted to the Applicant hereof.

When the hydraulic pump I is used in a known manner, each bore 12,within which slides a tubular piston 4, comprises a non-return valve atits end so that the pistons 4 together cause a pressurized flow (even ahigh pressure flow since 1000 bars can be exceeded with this type ofpump).

However, within the framework of the invention, none of the bores 12, inwhich the pistons 4 slide, comprises a non-return valve.

A pump II is associated with the pump I, immediately downstream of thelatter.

To each bore 12 of the pump I, in which a piston 4 slides, corresponds,in pump II, a chamber or bore 13 divided into two parts 13 a and 13 b bya flexible diaphragm 24 held in countercheck by a spring 15. Part 13 acommunicates directly with the end of the bore 12, whereas part 13 bisfitted, at its end opposite the diaphragm 24, with a suction valve 16and a delivery valve 17. All the valves 17 flow into a common pipe 18.

Preferably, as represented, each spring 15 bears against the rear sideof the diaphragm 24 via a collar 20. The shape of the collar 20 isdetermined in such a way that the bearing of the collar 20 against therear side of the diaphragm 24 does not deteriorate the latter in anyway.

The working thereof will be described hereunder:

When the primary shaft 2 is driven, the pistons 4 force the hydraulicliquid back into the chambers 13. The hydraulic liquid forced back intopart 13 a of the chamber 13 bears against the front side of thediaphragm 24, causing the latter to be displaced in the direction of thearrow f1 (FIG. 1). In moving, this diaphragm 24 forces back the liquidcontained in part 13 b of the chamber 13. This delivery is carried outvia the non-return valve 17.

Then, when the slated plate 1 continues to turn, the contact piece 5 ofeach piston 4 passes over the crescent 8, and this makes the chamber 13a, the inside of the tubular piston 4 and the suction chamber 9communicate with one another. At the very start of the stroke of thecontact piece 5 on the crescent 8, the pressurized liquid situated inthe chamber 13 a expands in the direction of the chamber 9; then, underthe effect of the spring 7 of the piston 4 and of the spring 15 of thediaphragm 24, the liquid situated in the chamber 13 a is forced backinto the bore 12 and from there onwards towards the chamber 9.

Thus, the hydraulic liquid, situated in the “dead” chamber at the end ofeach bore 12 when the piston 4 is at the end of its compression strokeand in the chamber 13 a, is renewed at the end of each compressioncycle, thus avoiding any heating of the liquid which would otherwise beinevitable. Moreover, this putting of the chamber 13 a and the chamber 9into communication with one another, at each cycle, materializes aresetting of the mobile elements to their initial position so that thevolume of hydraulic liquid forced back into the chamber 13 a remainsrigorously unchanged, with the inevitable leaks of the hydraulic pumpbeing returned into the chamber 9. By establishing communication betweenthe chambers 9 and 13 a, the drawbacks described above in “b” and “c”are remedied.

Displacement of the diaphragm 24 in the direction of the arrow f2 hasthe effect of drawing the product to be pumped into the part 13 b of thebore 13, via the non-return intake valve 16 (e.g., via inlet at 28, 28 ain FIG. 3), and of forcing back the hydraulic liquid situated in part 13a.

Thus, the product to be pumped is alternately subjected to suction thendelivery by the reciprocating motion of the diaphragms 24, this motionbeing caused by the variations in the volume occupied by the hydraulicliquid in the parts 13 a of the bores 13, these variations in volumebeing brought about by the alternated suction and delivery of thehydraulic liquid by the pistons 4 of the first pump I.

Each diaphragm 24 is subjected to the same pressure, on both its frontand rear side and evenly over the entire area of the diaphragm: on oneside, the pressure of the hydraulic “driving” liquid and on the otherside the pressure of the liquid forced back. The diaphragm is nottherefore subjected to any mechanical stress and cannot therefore betorn.

The pump embodying the invention is therefore a diaphragm pump in whicheach diaphragm is, during the delivery phase, subjected to the samepressure on each of its sides, which makes it possible to have adelivery pressure equal to the hydraulic pressure the first pump I iscapable of producing.

The pump embodying the invention can be used, among other things, topressurize liquids devoid of any lubricating power. In particular, itcan be used to supply injectors for an internal combustion engine(automobile engines) powered by premium fuel and/or liquefied petroleumgas (LPG), e.g., as a replacement fuel. The premium fuel is drawn in bythe valves 16, and delivered under pressure (over 50 bars) by the valve17 without the fuel ever being brought into contact with the metal partssliding against one another.

It should be noted that, at high pressures, liquids can no longer bedeemed incompressible. When a piston 4 reaches the end of its deliverystroke, the pressure of the hydraulic liquid is at its maximum. Asstated above, when the contact piece 5 is positioned at the start of thecrescent 8, the liquid, when it expands, will be delivered via thepiston 4, the passage 6 of the contact piece 5 and the crescent 8 intothe chamber 9; it will then be delivered by way of the effect of thespring 15. Though the compressed liquid is hot, the liquid in thechamber 9 and in the reservoir is not: thus, at each cycle, there willtherefore be a small exchange of liquid heated by compression andunheated liquid, thus ensuring the thermal balance of the first pump I.Preferably, though it is not represented, the cylindrical envelope 23 ofthe reservoir will be fitted with cooling fins.

In the case of the double pump embodying the invention being used, asstated above, to provide a high pressure supply to fuel injectors forengines, the engine oil itself can be advantageously used as hydraulicliquid by having the chamber 9 communicate directly with the engine oildistribution circuit, the temperature of this oil being regulated by theappropriate engine devices.

The pump embodying the invention can also be used for the pressurizedcirculation of drilling mud.

In fact, it can be used to pressurize any liquid whatsoever, includingcorrosive and aggressive liquids.

In the event of the hydraulic stage, pump I, being confronted with ahigh viscosity liquid, as is the case e.g., when used cold, it ispreferable, as is known, to have a mechanical means maintaining theheads 4 aof the pistons 4 on their contact pieces 5 during the suctionphase.

As explained above, the suction stress of the second pump II, which islinked to the power of the springs 15, enables the diaphragms 24 to bereturned to their initial position, due to the communication establishedwith the chamber 9.

Were it not for this return to the initial position, made possible forthis communication with the reserve of hydraulic liquid, there would bea risk of a slight drift occurring with each cycle of the pump.

This drift would rapidly generate a difference in volumes between thebore 12 and the part 13 aof the corresponding bore 13 which, in turn,would cause the diaphragms 24 to abut, and the pump to break immediately(either at the level of the first pump I or at the level of the secondpump II).

Thus, it would appear that this zeroizing, or resetting to their initialposition of the mobile elements 24 of the second pump II, via thecrescent 8, is indeed crucial.

FIGS. 3 to 5 relate to an enhancement of the device in FIGS. 1 and 2 bymeans of which it will be possible to vary at will the flow rate of theliquid to be pumped.

When this liquid is fuel intended to power an engine, it can be ofinterest to vary the volume of fuel pumped by the pump II in order toadapt it to the running conditions of the engine.

For an engine to operate at full speed, the cubic capacity of the pumpmust be determined as a function of the extreme conditions of use of theengine, i.e., running at full speed and with a full load. This thusdefines the maximum pumping rate available at all times, so that, overand beyond these extreme conditions of use, the pump supplies a surplusrate which is returned to the reservoir.

However, fuel that is thus returned to the reservoir has been heated bycompression, as a result of which hot fuel is constantly being returnedto the reservoir. As the reservoir gradually empties, the fuel becomesincreasingly hot whence a risk of having unwanted fuel vapors appear inthe reservoir, and these have become difficult to treat due toincreasingly strict standards especially as regards direct fuelinjection engines.

It has therefore proved necessary to modulate the pumping rate accordingto engine requirements.

The first solution consists in manufacturing the first pump I, in theform of a variable rate pump, by using a slanted plate of variable slantas is the case in certain pumps manufactured by the Applicant hereof.

However, such a pump risks being too costly for large scale seriesproduction of automobiles, as a result of which a second solution isdescribed below.

The device according to this second solution comprises a double pumpsuch as the one disclosed in patent application No. 96.07043, but inwhich each piston of the hydraulic pump is lifted with a means enablingcancellation of all or part of the flow rate pumped by the pump.

FIGS. 3 and 4 illustrate a double pump similar to those in FIGS. 1 and 2in which the same elements bear the same references.

In reference to these figures, each tubular piston 4 can be seen to becompletely passed through by a pipe 30.

Furthermore, the pistons 4 are borne by two support members 31 and 32drilled with orifices in which the pistons slide. The orifices drilledin the support member 31 are designated by the reference 33, whereas theorifices drilled in the support member 32 constitute the above-mentionedcylinders. To this end, the thickness of the support member 32 isgreater than the maximum stroke of the pistons 4.

The space included between the support members 31 and 32 constitutes anannular chamber 35.

In this space 35, each piston 4 is partially covered by a sliding liner34. These sliding liners are all connected to a control rod 38 in orderto be capable of all sliding together between two extreme positions, thefirst of which is illustrated in FIG. 3 and the second of which isillustrated in FIG. 4.

In the position represented in FIG. 3, the liners 34 obstruct thedrilled holes 36 which establish communication between the internal pipe30 of each piston 4 and the annular chamber 35. In the positionrepresented in FIG. 4, the liners 34 reveal the drilled holes 36.

The springs 7 of FIGS. 1 and 2, whose function is to maintain the pistonheads held against their sliding contact pieces 5, are replaced by atappet 7 b which acts on a flange 4 b bearing against the rear side ofeach piston head 4. The tappet 7 b is held in countercheck by a spring 7a.

The tappet 7 b, holding the flange 4 b of each piston head incountercheck, is passed through by a pipe 37 establishing communicationbetween the two chambers 9 and 35.

Thus, when, under the effect of the control rod 38, the liners 34 are inthe position represented in FIG. 4, the hydraulic liquid forced back byeach piston 4 flows back, via the pipes 30 and 36, to the annularchamber 35 and from there, via the bore 37, into the chamber 9 andinlet/outlet 9 a. It ensures that the flow rate of the hydraulic pump Iis zero, and therefore that the diaphragms are motionless and do nothave any pressurized suction or delivery effect on fuel to theinjectors; the fuel flow rate towards the injectors is therefore alsozero.

When, under the effect of the control rod 38, the liners 34 are in theposition represented in FIG. 3, the bores 36 are obstructed by theliners and the flow rate of the hydraulic pump I is at its maximum. Itensures that the fuel flow rate to the injectors is also at maximum.

Between these two extreme positions all the intermediate flow rates canbe obtained as a function of the position of the liners 34, the positionbeing determined by the position of the rod 38 which is controlled bythe running of the engine by any appropriate monitoring means.

It ensures that the output rate of the pump I is regulated as a functionof the fuel flow rate required for the injection and that surplus fuelreflux to the reservoir is kept as low as possible.

It should be noted, however, that the fuel flow rate thus obtained is apulsated rate. In fact, if, for instance, the liners 34 are in aposition such that only 10% of the maximum rate of the pump I is beingsupplied into the part 13 a of the volume 13, this means that the pump Idoes not have any output during 90% of the stroke of each piston, orthat there is only an output during 10% of the stroke of each piston.The flow rate is thus effectively a pulsated flow rate.

This causes a drawback that must be remedied.

To this end, a device is placed, downstream of the outlet 29 andupstream of the injectors, to eliminate these pulsations. This devicecan advantageously be constituted in a manner similar to a hydraulicaccumulator, i.e., constituted by a capacity having a volume that ishigh in relation to the flow rate supplied to the injectors andmaintained at a constant pressure.

The injection rate thus obtained corresponds exactly to the fuelrequirements of the engine, without any reflux to the reservoir as thisrate is regular, i.e., devoid of pulsations.

FIG. 6 represents a pump similar to the pump in FIG. 1, in which thesame elements bear the same references.

The reservoir 11 of FIG. 1, which surrounds the hydraulic pump, isreplaced by an exterior reservoir 11 a that communicates with thechamber 9 via a pipe 10; otherwise all the other components areidentical, with the exception of the diaphragm of the pump II in FIG. 1.

In the pump in FIG. 1, each volume 13 is divided into two parts 13 a, 13b by a diaphragm 24 thrust back by a spring 15 resting against thediaphragm 24 by means of a collar 20.

In the pump in FIG. 6, the individual diaphragms 24 are replaced by asingle diaphragm 44 which, at the level of the chambers 13, will becomedeformed so as to partially penetrate the volume 13 against thecorresponding spring 15.

More precisely, the pump of FIG. 1, as that of FIG. 6, comprises amonobloc pump housing 40, in two cylindrical portions 40 a and 40 b,portion 40 b having an inside diameter greater than that of portion 40a. In the portion 40 a are arranged the bearings 3, the primary shaft 2,the slanted plate 1, the supply chamber 9 and the rear portion 41 a of apart 41 in which the bores 12 are drilled. The front portion 41 b ofthis part is located in the portion 40 b of greater diameter of thehousing 40 so that this front part 41 b rests on the shoulder separatingthe two portions 40 a and 40 b of the housing 40. The bores 12 of thepistons 4 open out on the front side of this portion 41 b. A circularplate 42 is arranged against the portion 41 a and is locked intoposition in relation thereto by means of a pin 42 a. This plate 42comprises as many drilled holes 43 as there are bores 12 and chambers13. The chambers 13 are made in a part 45 which is screwed to the openend of the portion 40 b of the housing 40. Between the part 45 and theplate 42 is located a diaphragm 44 which is in the shape of a disk ofthe same diameter as the plate 42. The diaphragm 44 is cramped betweenthe plate 42 and the end of the part 45. Each drilled hole 43communicates with a bore 12 of the pump I and is situated opposite avolume 13.

When a piston 4 forces back hydraulic liquid under high pressure, thisliquid will be forced out of the bore 12, into the drilled hole 43 andwill deform the portion of the diaphragm 44 located opposite thecorresponding chamber 13, this deformation acting against the spring 15bearing against the other side of the diaphragm by means of the collar20. The liquid to be pumped and which is situated in the chamber 13(behind the collar 20) is forced back via the non-return valve 17. Whenthe piston 4 retreats in its bore 12, the portion of the diaphragm 44which had become deformed and partially penetrated the volume 13, ispushed back by the spring 15 and returns to its initial shape whileexerting suction on the liquid to be pumped via the non-return valve 16.

As in the previous cases, there is direct communication between thedrilled hole 43 and the chamber 9 via the crescent 8.

FIG. 9 represents another embodiment of the pump in FIGS. 6 to 8.

In this embodiment, the essential difference concerns the mechanicalconstitution of the hydraulic pump I.

This hydraulic pump I comprises, like the pumps in FIGS. 1, 3 and 6, aslanted plate 1 against which tubular pistons 4 rest through theintermediary of sliding contact pieces 5 drilled with a bore 6 intendedto come and move over a crescent 8. However, in the pumps previouslydescribed, the slanted plate 1 is located at the end of a primary shaft2 borne by bearings 3; whereas in the pump in FIG. 9, the slanted plate1 is integrated into a ball bearing.

This ball bearing comprises an outer cap 61 secured inside the housing60 of the pump, and an inner cap 62 to which the slanted plate 1 issecured, a set of balls 63 being located between the two caps 61 and 62.At its rear part, the slanted plate 1 comprises a seat 64 into which theend of a primary shaft (not represented) can slot.

The pump II is identical to the one described in relation to FIG. 6, thesame elements bearing the same references.

The only difference stems from the fact that the non-return suctionvalves 16 are eliminated and that it is the diaphragm 44 itself which isused to fulfill the role of the non-return valves.

In reference to FIG. 9a, which is an enlarged view of a portion of FIG.9, it can be seen that with each chamber 13 is associated a conduit 50connected to a chamber 51 into which the liquid to be pumped arrives viaa conduit 52. The conduit 50 is drilled through the mass of the part 45and opens out, at its end opposite the chamber 51, against the diaphragm44. The plate 42—which is positioned between the part 41, in which thebores 12 of the pistons 4 are made, and the part 45 in which thechambers 13 are located—comprises two seats 53 and 54 connected by aconduit 55. The seat 53 is hollowed out of the face of the part 42 whichis in contact with the diaphragm 44, whereas the seat 54 is hollowed outof the face which is in contact with the part 41. The configuration ofthe seat 54 is such that the latter communicates with the bore 12, andthe seat 53 extends to the level of the chamber 13.

Thus, when the pressurized liquid is forced back by a piston 4, thepressurized liquid arrives via the seat 54 and the conduit 55 into theseat 53 and the diaphragm is applied, by the hydraulic pressure, againstthe orifice of the conduit 50 which is thereby obstructed. Conversely,when the piston 4 is in the suction phase, the motion of the collar 20,which pushes the diaphragm back, moves the latter away from the orificeof the conduit 50. As the diaphragm 44 is rammed against the bottom ofthe seat 53, this clears a space 56 between the diaphragm 44 and thewall of the part 45, and the space 56 ensures communication between theconduit 50 and the chamber 13 thus enabling the liquid to be pumped tobe admitted into this chamber.

Preferably, the liquid to be pumped (which is e.g., automotive fuel)should arrive via the pump 52 at a low pressure, of the order of 1 to 2bars, provided by a known type of electric pump so that, once thehydraulic pressure disappears from the seat 53, the diaphragm 44 will bethrust back to clear the passage 56.

It is also preferable that, at the level of each conduit orifice 50, thediaphragm 44 be fitted with a reinforcing collar 57, of wider diameterthan the orifice, whose purpose will be to avoid the diaphragm beingthrust, by the pressure exerted, into the orifice of the conduit 50 andthus being subjected to deterioration.

It is also advantageous to shape the diaphragm by molding in such a waythat, at rest, in the absence of any pressure, it fills the seat 53 andclears the passage 56.

Thus, in deforming itself between a position in which it is situated atthe bottom of the seat 53 and a position in which it obstructs thesuction conduit 50, the diaphragm 44 plays the role of non-returnsuction valve.

The conduits 50, seat 53, conduit 55, seat 54 will, of course, be asnumerous as the bores 12 and chambers 13.

The arrangement thus described in reference to FIGS. 9 and 9a isindependent of the configuration of the hydraulic pump I and can betransposed to the pump of FIGS. 6 to 7 as represented in FIG. 9.

In all the examples represented in FIGS. 1 to 9, the hydraulic pump I isan oscillating plate or slanted plate pump and the pistons are axialpistons.

However, it should be remarked that the same result can be obtained witha radial piston pump provided the pistons are tubular and provided theheads thereof rest against the drive cam (fulfilling the same role asthe slanted plate 1) by means of sliding contact pieces which come andmove over a crescent; so that, at the end of each compression cycle, thechamber in which the diaphragm moves is made to communicate directlywith the hydraulic liquid admission chamber.

Such a radial piston pump is represented in FIG. 11.

This pump comprises a cam 101, which is an eccentric borne by a primaryshaft 102 itself borne by bearings 103. Each piston is a tubular piston104 held in countercheck by a spring 107, so that its head 104 a restsagainst the cam 101 via a sliding contact piece 105 passed through by anorifice 106. The cam 101 moves about in a chamber 109 communicating witha reservoir of hydraulic liquid (not represented). Communication betweenthe chamber 109 and the interior of each tubular piston 104 isestablished when the contact piece 105 moves over the groove 108hollowed out in the cam 101.

The pump II is identical to the one in FIG. 1, and the same elementsbear the same references.

The cam 101 corresponds to the slanted plate 1; the pistons 104correspond to the pistons 4; the contact pieces 105 to the contactpieces 5; the groove 108 to the crescent 8 and the chamber 109corresponds to the chamber 9.

The operation of the double pump (I-II) represented in FIG. 10 isidentical to that of the pumps previously represented.

What is claimed is:
 1. A pump including a first hydraulic pump componentin fluid communication with a second pump component, wherein the firsthydraulic pump component comprises: a hydraulic fluid chamber, at leastone piston in intermittent fluid communication with the hydraulic fluidchamber, the at least one piston being a tubular piston defining apiston chamber therein that receives hydraulic fluid from the hydraulicfluid chamber, the piston comprising (1) a piston head abutting theslanted plate via a sliding contact piece, wherein the sliding contactpiece includes a bore therein in fluid communication with the pistonchamber, and (2) a spring engaging the piston head, a slanted platepiston driving mechanism coupled with the at least one piston, thepiston driving mechanism reciprocating the piston between a suctionposition and a delivery position, and the spring urging the pistontoward the suction position, wherein the piston driving mechanismcomprises a crescent opening therein in fluid communication with thehydraulic fluid chamber and in intermittent fluid communication with thepiston chamber of the tubular piston when the driving mechanismreciprocates the piston from the delivery position toward the suctionposition; and wherein the second pump component comprises: at least onepump chamber, corresponding to the at least one piston, including aflexible diaphragm therein dividing the pump chamber into a pumpingsection and a delivery section, the pumping section of the pump chamberbeing in fluid communication with the piston chamber of the tubularpiston such that the flexible diaphragm is reciprocated by displacementof hydraulic fluid by the first hydraulic pump and such that when thedriving mechanism of the first hydraulic pump reciprocates the pistonfrom the delivery position toward the suction position, the pumpingsection, the piston chamber and the hydraulic fluid chamber are in fluidcommunication with one another.
 2. A pump according to claim 1, whereina circular plate is placed between a first part in which a borereceiving the at least one piston is located and a second part in whichthe pump chamber is located, and wherein communication between the boreand the pump chamber is established by way of drilled holes in thecircular plate.
 3. A pump according to claim 1, wherein the slantedplate is a plate with variable inclination.
 4. A pump according to claim1, further comprising a pump housing, wherein the slanted plate pistondriving mechanism further comprises a ball bearing assembly including anouter cap secured to the pump housing and an inner cap securing theslanted plate.
 5. A pump according to claim 1, further comprising meansfor varying the flow rate of the first hydraulic pump component and,therefore, the rate of the second pump component.
 6. A pump according toclaim 5, wherein the varying means comprises openings that can becompletely or partly blocked off by a mobile liner moved by a controlunit.
 7. A pump according to claim 6, wherein the first hydraulic pumpcomponent comprises two pistons slidably supported in two supportmembers, respectively, drilled with orifices and separated from eachother by a flow chamber, and wherein the mobile liners are disposed inthe flow chamber and are shiftable between a maximum pump rate positioncovering the openings and a zero pump rate position clear of theopenings.
 8. A pump according to claim 7, wherein the liners areshiftable to intermediate positions between the zero pump rate positionand the maximum pump rate position.
 9. A pump according to claim 8,wherein the liners are coupled to a common control unit which is drivenby a control device.
 10. A pump according to claim 9, wherein a dampingdevice is located downstream of an outlet of the second pump component.11. A pump according to claim 1, wherein the second pump componentfurther comprises a spring engaging the flexible diaphragm via a collarin the delivery section.
 12. A pump according to claim 11, wherein theflexible diaphragm acts as a suction valve and wherein the second pumpcomponent further comprises a delivery valve in the delivery section ofthe pump chamber, the flexible diaphragm and the delivery valve workingcooperatively to draw and deliver a product to be pumped.
 13. A pumpaccording to claim 12, wherein an intake conduit for the product to bepumped opens out against the flexible diaphragm which is held against anorifice of said conduit during a delivery phase, and is removedtherefrom during a suction phase.
 14. A pump according to claim 13,wherein the portion of the flexible diaphragm bearing against the intakeconduit is fitted with a reinforcing collar.
 15. A pump according toclaim 13, wherein, during the suction phase, the flexible diaphragm fitsinto the bottom of a seat in order to clear a passage for communicationbetween the intake conduit and the pump chamber.
 16. A pump according toclaim 15, wherein the flexible diaphragm is performed by molding tooccupy the bottom of the seat, during the suction phase, in order toclear the passage.
 17. A pump according to claim 1, wherein the secondpump component further comprises a suction valve and a delivery valve inthe delivery section of the pump chamber, the suction valve and thedelivery valve working cooperatively to draw and deliver a product to bepumped.
 18. A pump according to claim 17, wherein the second pumpcomponent further comprises a spring engaging the flexible diaphragm inthe delivery section, the spring urging the diaphragm toward a productdrawing position, wherein when the driving mechanism of the firsthydraulic pump reciprocates the piston from the suction position towardthe delivery position, the flexible diaphragm is deflected against thespring toward a product delivery position, thereby reducing a volume ofthe delivery section of the pump chamber.
 19. A pump according to claim18, wherein the spring rests against a rear side of the flexiblediaphragm via a collar shaped so as not to deteriorate said rear side ofthe diaphragm.
 20. A pump according to claim 1, further comprising ahydraulic fluid reservoir in fluid communication with the hydraulicfluid chamber.
 21. A pump according to claim 20, wherein the reservoiris on the exterior of the first pump component and communicates with thefirst pump component by a pipe leading into the hydraulic fluid chamber.22. A pump according to claim 20, wherein the reservoir is constitutedby a cylindrical envelope surrounding the first pump component andcommunicating with the hydraulic fluid chamber by a plurality oforifices.
 23. An internal combustion engine including fuel injectorsreceiving high pressure fuel from a pump including a first hydraulicpump component in fluid communication with a second pump component,wherein the first hydraulic pump component comprises: a hydraulic fluidchamber, at least one piston in intermittent fluid communication withthe hydraulic fluid chamber, the at least one piston being a tubularpiston defining a piston chamber therein that receives hydraulic fluidfrom the hydraulic fluid chamber, the piston comprising (1) a pistonhead abutting the slanted plate via a sliding contact piece, wherein thesliding contact piece includes a bore therein in fluid communicationwith the piston chamber, and (2) a spring engaging the piston head, aslanted plate piston driving mechanism coupled with the at least onepiston, the piston driving mechanism reciprocating the piston between asuction position and a delivery position, and the spring urging thepiston toward the suction position, wherein the piston driving mechanismcomprises a crescent opening therein in fluid communication with thehydraulic fluid chamber and in intermittent fluid communication with thepiston chamber of the tubular piston when the driving mechanismreciprocates the piston from the delivery position toward the suctionposition; and wherein the second pump component comprises: at least onepump chamber, corresponding to the at least one piston, including aflexible diaphragm therein dividing the pump chamber into a pumpingsection and a delivery section, the pumping section of the pump chamberbeing in fluid communication with the piston chamber of the tubularpiston such that the flexible diaphragm is reciprocated by displacementof hydraulic fluid by the first hydraulic pump and such that when thedriving mechanism of the first hydraulic pump reciprocates the pistonfrom the delivery position toward the suction position, the pumpingsection, the piston chamber and the hydraulic fluid chamber are in fluidcommunication with one another.
 24. An internal combustion engineaccording to claim 23, wherein the hydraulic fluid chamber is an engineoil reservoir.
 25. An internal combustion engine according to claim 23,further comprising a damping device located downstream of an outlet ofthe second pump component and upstream of the fuel injectors, thedamping device having a capacity of sizable volume in relation to anengine fuel rate maintained at an injection pressure.